This invention relates to methods and apparatus for the detection of chemically-bound nitrogen in organic compound samples. More particularly, this invention relates to the detection of chemically-bound nitrogen in an organic chemical compound utilizing chemiluminescent detection techniques.
The oldest and most widely used procedure for the analysis of chemically-bound nitrogen is the Kieldahl method. Most often this method is used to obtain indirectly the protein content of foods and biological species. The method involves degradation and sulfation with heat, sulfuric acid and catalyst followed by neutralization, making strongly basic, distillation and tetration of the ammonia. Sometimes many hours are required to perform this analysis, and there has recently been found evidence that people performing the Kjeldahl analysis on a daily basis run hazardous health risks.
Later, a titration device was devised which complemented the Kjeldahl method in that trace quantities of nitrogen could be determined accurately and quickly. This particular method involved a pyrolysis and hydrogenation of a sample at high temperatures and in the presence of a nickel catalyst. The resulting ammonia was coulometrically titrated using a four-electrode hydrogen cell. Systems based on these methods are better known as micro-coulometric titrating systems. Such an electrolytic titration apparatus is shown in the prior art as U.S. Pat. No. 3,032,493 to D. M. Couslon, et al. However, certain disadvantages of couolometric titrating methods are apparent:
1. Ultra-high purity hydrogen is required; PA1 2. A high degree of special analytical techniques are necessary; PA1 3. Because of the use of hydrogen at high temperatures, there are certain questionable safety features of the method; PA1 4. A fairly low dynamic range is experienced.
More recently, chemiluminescent detection equipment for detecting chemically-bound nitrogen in the air have been developed. These chemiluminescent detectors are based on the reaction of nitric oxide with ozone to form metastable nitrogen dioxide (NO.sub.2 *). Almost instantaneously the excited nitrogen dioxide relaxes to its ground state with a resulting photo-emission (.epsilon.). Such a reaction is shown as follows: EQU NO+O.sub.2 .fwdarw.NO.sub.2 *+O.sub.2 EQU NO.sub.2 *.fwdarw.NO.sub.2 +.epsilon.
These chemiluminescent nitrogen detectors are commonly known as NO/NO.sub.z detectors. These detectors are utilized to detect ambiant nitric oxide and NO.sub.z concentrations in the air for sampling techniques and pollution control as approved by the Environmental Protection Agency. Such NO/NO.sub.z concentration meters are presently made by several companies, but they are limited in that they are able to detect chemically-bound nitrogen only as NO/NO.sub.z gases using a chemiluminescent detection technique in gas samples or air samples. They cannot be utilized with liquid or solid organic compound samples.
Accordingly, one primary feature of the present invention is to provide a chemiluminescent detector for chemically-bound nitrogen which may be utilized with samples that may be a gas, liquid, or organic solid.
Another feature of the present invention is to provide a chemiluminescent nitrogen detector which is simple to operate and the detection results are available in a matter of minutes.
Yet another feature of the present invention is to provide a chemiluminescent nitrogen detector which can provided a digital display that is proportional to the quantity of chemically-bound nitrogen detected in the sample.